Brother LH4-B800E Service Manual page 117

5. Troubleshooting guide
Cause
Thread take- Thread take-up spring
up spring tension and stroke
Rotary hook Needle height when
rotary hook point
aligned with needle
center
(Needle bar height and
needle bar rise)
Gap between needle
and rotary hook
Rotary hook lubrication
Thread twisted around
rotary hook
Needle Arm thread guide
thread take position
up
Bobbin case Damaged outside of
bobbin case
Bent bobbin holder
spring, etc.
5 - 2
Check
Adjust thread take-up
spring tension and
stroke
Adjust its timing
Three kinds of gauges
are available
For -2, for -3 and for -5
Adjust the gap
Adjust the quantity of
lubrication oil
Remove any twisted
thread from the inner
and outer rotary hook.
Adjust arm thread
guide position
Polish with buff
Replace the part
Solution
tension
W(0.1 - 0.2 N)
Loosen the tension or shorten the
stroke to such a degree that does
not cause double hooking
Adjust it while checking bar tacking
stitches
Adjust the needle bar height to "1"
on the gauge
Gauge
Adjust needle bar height to "2" on
the gauge
Widen the gap (0.01 - 0.08 mm) to
such a degree that rotary hook point
does not strike needle in zigzag
motion
Too small quantity of lubrication oil
will cause thread breakage
* Check the quantity of lubrication
as follows; When the number of
stitches is about 114, sew 20
stitches and using craft paper,
check that the number of splashed
oil spots is about 10
Adjust the center of screw to the
carved mark
Gap 0.5 mm
Use the B800E bobbin case.
LH4-B800E
stroke
4 - 6 mm
2.5 mm(-2, -5)
3.5 mm(-3)
0.01 - 0.08 mm
Carved mark
page
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(Instruction)
4-6
4-6
4-27
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